A plurality of circuit boards is tightly installed in a housing of an electronic device such as a communication device, a video device, a broadcasting device or the like. Electronic components that generate intense heat, such as semiconductor devices, a CPU (Central Processing Unit), FET (Field Effect Transistor), a power amplifier and the like, are mounted on each of the circuit boards. Accordingly, a cooling device for cooling the electronic device is required. The electronic components that generate intense heat, such as the semiconductor devices, the CPU, the power amplifier and the like, has a narrow temperature range of effective operation. Therefore, it is required to cool the electronic components individually, not the entire electronic device. As a consequence, in a recent cooling device for an electronic device, a cooling pipe through which a liquid coolant flows is provided close to each of the electronic components.
For example, in a water cooling type cold plate and a manufacturing method thereof of Patent Document 1, there is suggested a technique for improving a cooling efficiency by increasing a heat contact area between the water cooling type cold plate and a flat cooling pipe by attaching in a zigzag manner the flat cooling pipe to the water cooling type cold plate where the heating components are arranged.
Patent Document 1: Japanese Patent No. 3154247
In the water cooling type cold plate of Patent Document 1, a metal pipe having a circular cross sectional shape is extended in a zigzag shape. Next, at least a portion of the metal pipe which is inserted into an aluminum plate is planarized. The flat metal pipe is installed in a casting mold by a spacer and, then, molten aluminum is poured into the casting mold. Accordingly, the metal pipe having a zigzag shape is cast by the molten aluminum.
However, in the water cooling type cold plate of Patent Document 1, a bar member having a flat front surface and a flat rear surface is used as the spacer for positioning the metal pipe in the casting mold. Therefore, depending on a flowing direction of molten aluminum into the casting mold, the metal pipe is deformed by the stream pressure of the molten aluminum and misaligned with a heating component to be cooled. Accordingly, the cooling properties are not stabilized.